The invention discloses an excitation control system for a giant machine set, which comprises an excitation regulator cabinet, an excitation rectifier cabinet and deexcitation protection cabinet. The excitation control system is characterized in that: the excitation regulator cabinet comprises a human-computer interface, a first main controller, a second main controller, and a first industrial Ethernet switch and a second industrial Ethernet switch which form dual redundancy; the excitation rectifier cabinet comprises a thyristor rectification bridge, a cooling device, a peak absorbing deviceand a rectifier cabinet controller, wherein the rectifier cabinet controller transmits a pulse signal used for homogenizing current to control the thyristor rectification bridge and transmits a control signal to control the startup and stop of the cooling device, and the peak absorbing device absorbs commutating voltage of the thyristor rectification bridge; and the deexcitation protection cabinet comprises a deexcitation switch, a deexcitation resistor, a jumper and a jumper controller. The excitation control system for the giant machine set has the characteristics of high reliability, high transmission speed and high long-term stability.